Production of briquettes from calcined char employing asphalt binders and such briquettes



United States Patent ABSTRACT OF THE DISCLOSURE Carbonaceous briquetteshaving high mechanical strength and a homogeneous structure are producedfrom calcined coal char and a particular bituminous binder. The bindercomprises an asphalt obtained as a residue from the thermal cracking ofpetroleum oils, having an asphaltene content of from 40% to 85% byweight, a softening point of from 100 to 225 F., a carbon to hydrogenatomic ratio of from about 0.9 to 1.4, and being at least 90% soluble inbenzene.

This is a continuation-in-part of our copending application Ser. No.395,317, filed Sept. 9, 1964 and now abandoned.

This invention relates to briquettes produced from calcined coal charand a bituminous binder. In a more particular sense, the inventionpertains to the production of briquettes from calcined coal charparticles and a bituminous binder at least part of which is asphalthaving properties capable of imparting high mechanical strength to thebriquette whereby the latter is suitable for charging to metallurgicalfurnaces.

In the FMC Cope process disclosed and claimed in US. Patents 3,140,241and 3,140,242 granted July 7, 1964, bituminous coal, includingnon-coking coals, of a particle size less than 6 mesh and preferablyless than 16 mesh with the average particle size in the range of from 40to 60 mesh, is heated in the presence of oxygen, which may be derivedfrom the coal itself in the case of the socalled high oxygen-containingcoals, i.e., coals having an excess of by weight of oxygen, to atemperature high enough to drive off substantially all moisture butbelow that at which substantial amounts of tar-forming vapors evolve.Thereafter the coal particles from this heat treatment are heated to ahigher temperature at which tar-forming vapors are evolved and for atime interval sufficient to efiect polymerization of the heated coalparticles and evolution therefrom of substantially all of thetar-forming vapors to produce a char of markedly lower volatilecombustible material content than the parent coal and substantially freeof tar-forming vapors. This char is heated to a still higher temperatureto produce the calcined char particles for blending with the bituminousbinder.

The calcined char is mixed with the binder in the proportions of from75% to 90% calcined char to to 10% binder. These percentages are basedon the weight of the total mix. In this specification all percentagesand part values are given on a weight basis unless otherwise indicated.All mesh sizes are in terms of the United States Sieve Series (UnitedStates Bureau of Standards).

Preferred binders for the FMC Coke process are coal tar pitch or pitchesproduced by the condensation of tars from the gases evolved during thecarbonization and the subsequent dehydration, stripping, and/oroxidation of the resultant tars to produce pitches having a softeningpoint of from 100 to 225 F. (ASTM Ring and Ball).

The blend of calcined char and binder is compressed to 3,403,989Patented Oct. 1, 1968 produce the green briquettes which are then curedin an atmosphere containing oxygen to bring about copolymerization ofthe binder and the char so as to make the briquettes strong andinfusible. The cured briquettes are coked to produce briquettes suitablefor metallurgical purposes. The briquettes thus produced, when observedeven under a relatively low power magnification, are of uniformcomposition, i.e., as a general rule the carbon derived from thecalcined char and that derived from the bituminous binder areindistinguishable.

A more detailed description of the FMC Coke process is given in US.Patents 3,140,241 and 3,140,242, the disclosure of which is incorporatedherein by reference.

When producing briquettes from bituminous coals having insufficientvolatile matter to furnish enough tar to supply the binder requirementsfor the process, a supplemental source of a suitable binder must beused. Many bituminous binders, including paraffinic asphalts and someasphalts ordinarily used for making green briquettes, when used alone orwhen blended with the pitch binder derived from the tar produced in thecarbonization stage of the process are unsatisfactory because the binderwill not polymerize (or copolymerize) sufliciently well in the oxidativecuring step to harden the green briquette and cause it to becomeinfusible. In some cases, these unsatisfactory binders solidify duringoxidative curing, but they do not bond the char particles togethersufiiciently well to give a strong cured briquette. In either case, theresult is cured briquettes having low crushing strength which on cokingare unsatisfactory for metallurgical purposes.

It is accordingly a principal object of the present invention to providefor the calcined char a binder having such properties that is compatiblein all proportions with pitch binders derived from the tar obtained inthe carbonization stage of the process and which binder can be usedalone or blended with coal tar pitch binders heretofore used as a binderfor the calcined char and when so used alone or as a blend, results incured and coked briquettes having crushing strength and structure atleast as good as, if not better than, the crushing strength comparableof briquettes produced from the calcined char and coal tar pitch bindersheretofore employed.

Other objects and advantages of this invention will be apparent from thefollowing detailed description thereof.

We have found that the objects aforesaid can be realized by using atleast as part of the binder for the calcined char asphalts having anasphaltene content of from 40% to at least about of which asphalts aresoluble in benzene, a softening point of from to 225 F., preferably toF., a carbon to hydrogen (atom/ atom) ratio of from about 0.9 to 1.4,preferably from 1 to 1.3, obtained as a residue from the thermalcracking of petroleum oils. These asphalts will be hereinafter referredto as Asphalt Binders. They are compatible with coal tar pitch in allproportions. Hence they can be used to supply the deficiencies of tarproduction in any installation employing coals having insufficientvolatile matter to furnish enough ta-r to produce the pitch binders forbriquettin-g all of the calcined char produced.

The amount of Asphalt Binder blended with coal tar pitch bindersproduced from the tar recovered in the process in any given installationwill, in general, depend on the extent of the deficiency of the tarproduction of such installation. This will vary for each installationdepending chiefly on the coal treated, the recovery and processingequipment employed for recovering the tar and producing the pitch bindertherefrom, and the amount of binder employed within the range of from'10% to 25% in producing the briquettes. In general, a blend of pitchbinder and the Asphalt Binder containing up to 50% Asphalt Binder andthe rest pitch binder will give an adequate supply of binder for therequirements of the FMC Coke process taking into account variations inthe volatile content of available coals. The Asphalt Binder can be mixedwith the coal tar pitch binder in proportions of 95% to 5% AsphaltBinder, preferably 5% to 50%, and 5% to 95%, preferably 50% to 5% coaltar pitch binder having a softening point of 100 to 225 F. An allasphalt binder, rather than a blend with coal tar pitch, can be used, ifdesired, and results in good cured and coked briquetes having crushingstrength as good if not better than those produced from the samecalcined char using an all coal tar pitch binder. The use, however, ofall Asphalt Binder is not preferred, chiefly because of the economicloss involved when the tar produced in the process is not employed informing the binder and thus is not converted into briquettes.

By the asphaltene content of the asphalt is meant the proportion of theasphalt insoluble in n-pentane. The percentage values for asphaltenegiven herein were determined by ascertaining the proportion of theasphalt which remains undissolved after thorough mixing with n-pentane.

The oil content of the asphalt is that portion which is soluble inn-pentane and is not adsorbed from the pentane solution by activatedalumina. The resin content is soluble in n-pentane but it is adsorbedfrom it by activated alumina.

The Asphalt Binders used can be any of the commercially availableasphalts produced as residue from the thermal cracking of petroleum oilsby any of the several processes in use having an appreciable aromaticcontent and having the properties above set forth. Paraffinic asphalts,asphalts obtained as residues from the vacuum or steam distillation ofstraight run petroleum oils, and these asphalts thickened by air-blowingor oxidation are unsuitable.

Examples of satisfactory commercial asphalts which can be used asAsphalt Binders are the following:

(1) Asphalts having an asphaltene content of 78% to 81%, a resin contentof 3.5% to 4%, an oil content of to 18%, a softening point of about 150F., and a carbon to hydrogen atomic ratio of 1.28. These asphalts aresold by the Mobil Oil Company under the designation #B7206; they will bereferred to hereinafter as AB 1;

(2) Asphalts having an asphaltene content of 77% to 78%, a resin contentof 2% to 4%, an oil content of 19% to 20%, a softening point of about156 F., and a carbon to hydrogen atomic ratio of 1.22. These asphaltsare sold by the Mobil Oil Company under the designation #7060; they willbe referred to hereinafter as AB 11.

(3) Asphalts having an asphaltene content of 69% to 71%, a resin contentof 4% to 5%, an oil content of to 26%, a softening point of 139 F., anda carbon to hydrogen atomic ratio of 1.08. These asphalts are sold bythe Marathon Oil Company under the designation #63128; they Will bereferred to hereinafter as AB III.

All of these asphalts are produced as residues from the thermal crackingof petroleum oils; they contain appreciable amounts of aromatics and allare at least 90% soluble in benzene.

The Asphalt Binder is blended with the calcined char in the proportionsof from 75% to 90% calcined char and from 10% to 25% binder based on theweight of the total mix at a temperature of from 30 to 60 F. above thesoftening point of the binder. The blend is formed into shapeshereinafter referred to as briquettes by extrusion or briquetting underpressures in excess of 5000 psi. The maximum pressure usable anddesirable depends on the size of the shapes and the type of equipmentused. The resultant green briquettes are cured in an atmospherecontaining from 2.5% to 21% oxygen (e.g., air). Curing hardens andstrengthens the briquettes by converting the binder to an infusiblepolymer. As disclosed in said Patents 3,140,241 and 3,140,242, thecuring can be carried out at a temperature of from 450 to 500 F. for to180 minutes, preferably about two hours. The cured shapes, if desired,can be coked at temperatures above 1500 F. for at least five minutes inan atmosphere substantially free of carbon dioxide, water vapor andoxygen. At 1500 F. a minmum time of about 15 minutes is required; at1700 F. a minimum time of 10 minutes is required. At 1500 F. coking canbe continued for about one hour without loss of reactivity. At 1700 F.coking can be continued for about 40 minutes Without loss of reactivity.

The cured briquetes can be used if desired without subjecting them tothe coking treatment, when they are made by employing the Asphalt Binderalone or by use of a blend of the asphalt with coal tar pitch obtainedfrom the tar produced in the process, the blend being composed of anydesired proportions of the two components; the amount of Asphalt Binderblended with the coal tar pitch will depend on the deficiency of coaltar pitch binder. Cured briquettes are thus obtained which are infusibleand have adequate strength for use, for example, in cupolas and blastfurnaces. Actually the coking of these cured briquettes takes placewithin the furnace; the temperature conditions in cupola and blastfurnaces are such as to effect coking of the cured briquettes which arethen consumed in effecting the smelting and refining of the chargewithin the furnace.

By thus operating in accordance With the invention, the art is providedwith a method of preselecting an asphalt binder for use with calcinedcoal char whereby briquettes of consistently high mechanical strengthcan be realized. Moreover, it now becomes possible to utilize asphaltswhich were heretofore unsuitable as binders by blending them withasphalts whose parameters are in the upper range and thereby obtainblends or mixtures having the requisite physical and chemical propertiesset forth herein, namely a softening point Within the range of fromabout F. to about 225 F., preferably from about F. to about F., a carbonto hydrogen atomic ratio of at least 0.9, an asphaltene content of atleast 40%, at least 90% of which is benzene soluble.

Examples of asphalts not suitable as binder material when used along butwhich give satisfactory blends with asphalts having the upper range ofparameters are the following:

(a) Briquetting asphalts having an asphaltene content of 42.5%, a resincontent of 9.5%, an oil content of 48.0%, and a carbon to hydrogenatomic ratio of 0.728;

(b) Steam-refined asphalts having an asphaltene content of 41.5%, aresin content of 12.9%, an oil content of 45.6%, a softening point ofF., and a carbon to hydrogen atomic ratio of 0.716;

(c) The so-called dead level asphalts having an asphaltene content of34.8%, a resin content of 12.1%, an oil content of 53.1%, a softeningpoint of 144 F., and a carbon to hydrogen atomic ratio of 0.660;

(d) Paraffinic asphalts having an asphaltene content of 27.1%, a resincontent of 21.2%, an oil content of 51.7%, and a softening point of 140F.;

(e) Air-blown or oxidized asphalts having an asphaltene content of58.9%, a resin content of 13.3%, an oil content of 27.8%, a softeningpoint of 228 F., and a carbon to hydrogen atomic ratio of 0.676.

These asphalts (a) through (e) above) either do not solidify duringoxidative curing and/ or largely volatilize on subsequent coking to givea poorly bonded product.

The following examples are given to exemplify the present invention. Forcomparative purposes, there is also given the crushing strength anddescription of coke briquettes made with other binders.

In all cases the calcined char employed was produced from Elkol coal bythe FMC Coke process involving a three stage processing, namely,catalyzing, carbonizing and calcining, in fluid bed reactors asdisclosed in US. Patents 3,140,241 and 3,140,242. The calcined char thusproduced contained approximately 3 volatile matter on a moisture and ashfree basis, about 7% ash, and had a bulk density of 38.4 pounds percubic foot. The calcined char used had a particle size such that it allpassed through a 10 mesh screen.

In all cases by weight of binder was thoroughly mixed with the calcinedchar at a temperature of from 195 to 250 F., depending on the softeningpoint of the binder. Briquettes each weighing about 13 grams were madeby compressing the warm mix into a 1% inch ID cylinder at 15,000 p.s.i.,using a hydraulic hand press. The briquettes thus produced werecylinders 1% inches in diameter and about 0.8 inch high. They were curedin :air for 2 hours at 230 C. in a forced convection oven and then cokedfor minutes in an inert atmosphere at 950 C. in an electrically heatedrnuffie furnace. The curing was carried out in a wire mesh container toinsure good circulation of the current of hot air around the individualbriquettes.

The strength of the coke briquettes was measured by crushing thebriquettes in a Riehle Universal Testing Machine with the bottom platemovement set at 0.35 inch per minute. The load causing the firstdownward deflection of the indicator was taken as the crushing strength.The results reported are the average strength of five briquettes in eachbatch. The results are given in the tables which follows:

TABLE I.INVENTION Example Briquette N Binder strength,

I--. 5, 647 II 5, 441 IIL 5, 572 IV A blend of AB II and a paraflinlcasphalt 5,300

$53] Iribove), the blend containing 75.3% V A blend of AB I and theasphaltic residue 5,240

from an uncracked Wyoming crude (Mobil Oil Co. #B7208), the blendcontaining 41.0% AB I. VI Blend of AB I and topped coal tar binder 5,300

obtained from the earbonization oi Elkol coal, the blend containing 75%AB I and coal tar binder.

TABLE II.COMPARISON Briquette Test No. Binder strength,

p.s.i.

A Oxidized asphalt 2,920 B Asphalt from Wyoming crude, not cracked 3,370

(Mobil Oil Co. #137208). 0 Paratfinic asphalt ([d] above) 3, 516 Deadlevel asphalt ([0] above) 4, 046 Steam reduced asphalt ([b] above) 4,332 Briquetting asphalt ([a] above)- 4, 012

The briquettes thus produced by the present invention (Table I) were ofhomogeneous composition, that is, a fractured surface was smooth, withthe fracture plane going through rather than around the original charparticles, the fractured surface had a bright metallic lustre, andcarbon from the binder could not be readily distinguished from that ofthe original char particles. These coked briquettes had all of the otherdesirable properties of coke briquettes produced by the FMC Cokeprocess.

By contrast briquettes made from unsatisfactory binders (Table II), gavea surface fracture which was generally dull, black, and took place bypulling apart adjoining char particles. The original particles appearedto be part of a poorly cemented matrix. The crushing strength of thebriquettes made with the Asphalt Binder was somewhat greater than thosebriquettes made under the same conditions except for the use of the samerelative amount of coal tar pitch binder.

It will be noted from the above comparative data that the AsphaltBinders are unique. Surprisingly and unexpectedly, the Asphalt Bindersresult in coke briquettes having high crushing strength and ahomogeneous structure; an increase in the crushing strength of from 30%to 40% is obtained over and above the crushing strength of those cokebriquettes made under the same conditions but with petroleum derivedbinders not conforming to the specifications of this invention.

Why the Asphalt Binders should give such increase in the crushingstrength and so homogeneous a structure to the coked briquettes is notunderstood. It may be due to a high content of condensed ring aromaticcompounds indicated by the high asphaltene content and relatively highcarbon to hydrogen atomic ratio, which high content of condensed ringaromatic compounds results in better copolymeriza-tion with the calcinedchar during the curing treatment with consequent better bondedbriquettes upon subsequent coking. This explanation is advanced to givea better understanding of the invention; it will be appreciated that theinvention is not limited to this explanation.

The expression briquettes is used herein in a broad sense to includeextrusions and other shapes produced by blending the binder withcalcined char and shaping the resultant blend. The expression coal tarpitch" is used herein in a broad sense and includes topped or dehydratedtar binders from both low temperature and high temperature coal tars.

Since certain changes in carrying out the process of producingbriquettes and in the resultant briquettes which embody this inventioncan be made wtihout departing from the scope of this invention, it isintended that all matter contained in the above description shall beinterpreted as illustrative and not in a limiting sense.

What is claimed is:

1. The process of producing strong, infusible, homogeneous briquetteswhich comprises blending from 75% to 90% by weight of calcined charderived from coal with from 10% to 25% binder based on the weight of thetotal mix, the binder containing asphalt having an asphaltene content offrom 40% to by weight, at least of the asphalt being soluble in benzene,having a softening point of to 225 F., a carbon to hydrogen atomic ratioof about 0.9 to 1.4, and obtained as a residue from the thermal crackingof petroleum oils, subjecting the resultant blend to pressure to producegreen briquettes, and curing the green briquettes in anoxygen-containing atmosphere.

2. The process of claim 1, in which the asphalt binder has a softeningpoint of from to F. and a carbon to hydrogen atomic ratio of l to 1.3.

3. The process of claim 1, in which the binder for the calcined char isa mixture of coal tar pitch having a softening point of from 100 to 225F. and said asphalt.

4. The process of producing strong, infusible, homogeneous, carbonaceousbriquettes suitable for us as metallurgical coke which comprisesblending from 75% to 90% by weight of calcined char derived from coalwith from 10% to 25 binder based on the weight of the total mix, thebinder containing asphalt having an asphaltene content of from 40% to85% by weight, at least 90% of the asphalt being soluble in benzene,having a softening point of 100 to 225 F., a carbon to hydrogen atomicratio of about 0.9 to 1.4, and obtained as a residue from the thermalcracking of petroleum oils, subjecting the resultant blend to pressureto produce green briquettes, curing the green briquettes in anoxygen-containing atmosphere, and coking the cured briquettes at atemperature above 1500 F. in an atmosphere substantially free of carbondioxide, water vapor and oxygen for at least five minutes.

5. Carbonaceous briquettes having high mechanical strength and ahomogeneous structure and which are infusible, constituted ofcarbonaceous material derived from coal and a bituminous binder, saidbinder being derived in part at least from an asphalt having anasphaltene content of from 40% to 85 by weight, a softening point offrom 100 to 225 F., a carbon to hydrogen atomic ratio 7 of from about0.9 to 1.4, at least 90% of Said'asphalt being soluble in benzene, saidasphalt being obtained as a residue from the thermal cracking ofpetroleum oils.

6. carbonaceous briquettes as defined in claim 5 in which the saidasphalt has a softening point of from 130 to 160 F. and a carbon tohydrogen atomic ratio of from 1 to 1.3.

7. Carbonaceous briquettes as defined in claim 5 in which the binder isderived from a mixture containing from 5% to 95% by weight of coal tarpitch and from 1 95% to 5% by weight of said asphalt.

References Cited UNITED STATES PATENTS Mead 44-23 Mack 20822 Brown 44-23Reerink et al 4423 Gorin et a1 44-19 XR DANIEL E. WYMAN, PrimaryExaminer.

C. F. DEES, Assistant Examiner.

